This invention pertains to the field of on-board signals responsive to the speed of vehicles. Within that field it relates to signals that are activated when the vehicle exceeds a predetermined speed and that remain activated when the vehicle speed is then reduced below the predetermined speed. In particular, it is in the class of such signals that are constituted so that they may be deactivated or otherwise nullified only by a means that can be used to cause some penalty to the driver of the vehicle.
The prior art contains devices in which the signal forms a permanent record such as a counter that is incremented, or a recording medium that is marked, by each incident of excessive speed. These signals cannot be deactivated but they can be nullified by enforcement authorities who may extract a penalty, such as a fine, on the basis of the record and then provide certification of nullification so that one incident of speeding cannot again be penalized.
In another class of enforcement signals known in the prior art, the signal can be deactivated but only by equipment that is intended to be possessed only by enforcement authorities.
There is also in the prior art a class of signals that are accompanied by physical actions that in themselves provide penalties. One example is a device that shuts off the vehicle engine for a period of time. Another is a device that, upon excessive speed, blows fuses that are necessary for normal operation of the vehicle and for which replacements are intended to be obtainable only from enforcement authorities.
No on-board enforcement signal means can be expected universally to be effective in reducing incidents of speeding unless its installation is mandatory. While this is a political rather than a technical matter, political considerations may be affected by: cost of both the on-board equipment and any auxilliary equipment or record keeping required; convenience and ease of use; reliability and maintainability; tamper resistance; and whether any physical penalty accompanying the signal introduces in itself a possible hazard. For this reason it is worth considering alternative enforcement signal means that may, upon installation, be less effective or demand less severe penalties but that may be more likely to become politically acceptable.
My U.S. Pat. No. 4,250,487 discloses an enforcement signal that is deactivated after a fixed time interval after the vehicle stops. The penalty is merely to stop and then avoid detection of the signal until the time runs out. But the vehicle may be driven, below the threshold speed to prevent signal reactivation, during the period of detection avoidance while the timer runs out.
The present invention is an improvement that prevents deactivation of the signal unless the vehicle remains at rest for the entire fixed time interval.